1. Field of the Invention
This invention relates to a wiping nozzle for use in a wiping apparatus on a hot dip galvanizing line for coating zinc or the like.
2. Description of the Related Art
In such a type of wiping apparatus, a surplus of molten zinc adhering to the surface of a strip (steel sheet or plate) exiting from a molten metal coating pot and traveling upward is removed by being wiped with a gas blown from a pair of wiping nozzles (gas wiping apparatus) opposingly installed above the molten metal coating pot, for example.
With such a gas wiping apparatus, a quality defect (coating irregularities, streaks, etc.) occurs on the surface of the strip after coating, if there is a scar on the wiping nozzle due to contact with the strip, or the deposition of the molten metal on the wiping nozzle (i.e., stain) attributed to a splash. This requires maintenance work including the replacement of the wiping nozzle. Alternatively, plural types of nozzles may be replaced in accordance with the quality of coating.
In such a case, the following operation as shown in FIG. 9 has been common practice with the conventional gas wiping apparatus: A strip S is cut above a molten metal coating pot 102, and a lower piece of the strip S cut is sunk in the molten metal coating pot 102, with the leading end of the strip being secured by a chain or the like. In this state, wiping nozzles 100a, 100b are lifted above the molten metal coating pot 102 by a moving crane or wires 101a, 101b, and moved out of a coating device such as the molten metal coating pot 102 so that maintenance, including replacement, of the wiping nozzles 100a, 100b is performed.
When a wiping nozzle 100a1 in operation is to be replaced by a wiping nozzle 100a2 placed in a wait state in the case of a turret nozzle, as shown in FIGS. 10A to 10C, the following motions have been made: (1) the nozzles retracted (see FIG. 10A→FIG. 10B)(2) the nozzles lifted (see FIG. 10B→FIG. 10C)(3) the nozzles rotated (see FIG. 10C)(4) the nozzles lowered (see FIG. 10C→FIG. 10B)(4) the nozzles advanced (see FIG. 10B→FIG. 10A).
In a case as in Patent Document 1, moreover, a pair of wiping nozzles are integrated with other wiping equipment via the base of a frame to form a wiping equipment assembly. In performing its maintenance including replacement, a strip is cut above a molten metal coating pot, and a lower piece of the strip cut is sunk in the molten metal coating pot by means of a chain or the like, as in FIG. 9. In this state, the wiping equipment assembly including the wiping nozzles is lifted by a moving crane or the like, and carried out of plating equipment (out of the line).